Roads and highways represent one of the most important anthropogenic impacts on natural areas and contribute to habitat fragmentation, because they are linear features that can inhibit animal movement, thereby causing barrier effects by subdividing the populations adjacent to the roads. The study presented here aims to determine, to which extent roads act as a barrier, subdividing populations of three species of small forest mammals: bank vole, yellow-necked mouse and common shrew, and what is the relative importance of road width and traffic intensity on the barrier effect. The study was carried out at four 25 m long segments of roads, close to the city of České Budějovice. All segments crossed a forest. The capture-recapture method was applied to determine the crossing rates of animals. The traps were checked three times each day during four consecutive nights, in summer and in autumn. We found that: (1) roads strongly prevent crossing movements in all three studied species, (2) there are interspecific differences in road crossing rates, (3) species cross more often narrow than wide roads, (4) traffic intensity does not affect the crossing rates.
We investigated, in a laboratory experiment, how natural food available in autumn influences the body mass, locomotor activity, and level of detoxification enzymes in the bank vole Clethrionomys glareolus (Schreber, 1780). In September and October 2001, two groups of bank voles were fed with herbs and acorns. A well-balanced mixed diet was a control. The animals fed with herbs showed high locomotor activity, compared to those fed control diet, a distinct increase of food consumption but loss of body mass. These voles also showed remarkably increased levels of detoxification enzymes (cytochrome P-450 and glutathione transferases) in their livers. Bank voles fed with acorns also lost weight and were more active, compared to the control (but less than the herb-fed group), and had higher levels of detoxification enzymes. Bank voles fed with the control diet showed the lowest level of locomotor activity and did not lose weight. We explain the increased activity of bank voles with stress response to low-quality food, especially as this effect ceased after changing the diet to the control one. Our results suggest that poor nutritional quality of herbs, the bank voles’ main food under natural conditions, may be the main cause of seasonal decline in vole density in autumn-winter.
Between 1996 and 1998, microhabitat selection by three small mammal species was studied in oak-elm forest using the catch-mark-release (CMR) method. Microhabitat selection by these species was assessed by Discriminant Function Analysis (DFA) and Canonical Correspondence Analysis (CCA). Apodemus flavicollis was shown to prefer dense young forest and shrubs, but the presence of dead woody material was also important. In Microtus arvalis the data confirmed a negative relationship with stands with higher tree and shrub cover and a preference for open meadows. Clethrionomys glareolus was found to prefer non-fragmented tree microhabitats, preferring sites with developed undergrowth and ample hiding places amongst fallen logs and branches. Although C. glareolus did not change its microhabitat requirements during the year (spring to autumn), within forest stands it was connected with undergrowth regardless of species composition; this highlights the importance of undergrowth for C. glareolus. Seasonal changes in microhabitat selection could not be confirmed unambiguously.